package servlet;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.sql.*;
import java.util.ArrayList;
import pojo.User;
import java.util.List;

@WebServlet(urlPatterns ={ "/user"})
public class UserServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        List<User> users =new ArrayList<>();
        //jdbc 操作数据库
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");

            // 2.获取连接(url username password)
            String url="jdbc:mysql://127.0.0.1:3306/jdbc?characterEncoding=utf-8";
            Connection connection = DriverManager.getConnection(url, "root", "123456");
//            if(connection!=null){
//                System.out.println("连接成功");
//            }

            // 3.写sql
            String sql="select * from user";

            // 4.预编译sql
            PreparedStatement preparedStatement = connection.prepareStatement(sql);

            // 5.有参数设置参数

            // 6.执行sql
            ResultSet resultSet = preparedStatement.executeQuery();

            // 7.遍历结果集
            while (resultSet.next()){
                User user = new User();
                user.setId(resultSet.getInt(1));
                user.setName(resultSet.getString(2));
                user.setPass(resultSet.getString(3));
                // 把对象添加到集合中
                users.add(user);
            }

            // 8.关闭资源
            resultSet.close();
            preparedStatement.close();
            connection.close();

            //把集合中的数据存储到作用域中
            req.setAttribute("users",users);
            //打开页面
            req.getRequestDispatcher("/user.jsp").forward(req,resp);

        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }
    }
}
